Visitors to the website Friday afternoon saw a notice indicating various Backpage sites were taken over in an “enforcement action” brought by the FBI, the Postal Inspection Service and the IRS.

Authorities reportedly brought criminal charges against seven of those involved in operating the site.

The FBI reportedly raided homes of the site's co-founders, Michael Lacey and James Larkin in Sedona, Arizona, according to KNXV, an ABC affiliate in Phoenix. Its owners are also at the center of a federal money laundering case.

Similar to Cragslist, Backpage is a basic classified ads site where people can buy, sell or trade everything from cars to furniture. But the site features racy adult sections, such as escorts and body rubs. Law enforcement says it's code for prostitution and sex trafficking, largely targeting women and children.

"Backpage and other sites have been profiting off people who have been trafficking those minors," Beaverton Police Detective Chad Opitz told KATU.

Opitz is the agency's leading sex crimes detective. Many of his investigations involve criminal activity through Backpage. He says he's rescued victims and arrested those who use it for the wrong reasons.

"[It's] been a valuable tool in focusing in on and identify those victims of sex trafficking," Opitz said.

While he views the seizure as a win, he says criminals will resort to other means.

Opitz looked to the example of the Silk Road, an online black market known as a platform for selling illegal drugs. The website was launched in February 2011, then shut down twice by the FBI in 2013 and 2014. Opitz says drug dealers still found ways to push their product. He fears the same will happen following the seizure of Backpage; the void will be filled by something else.

"The ones that really want to take advantage of people, and exploit the youth, will find another way to do it," Opitz said. "Prostitution has been around pretty much since the beginning of man, and unfortunately it will continue to be."

While it may make the crimes harder to follow and fight, Esther Nelson, executive director of Safety Compass, a local nonprofit that helps survivors of the commercial sex industry, says about 90 percent of its client base was trafficked through Backpage.

"Backpage essentially acted as a pimp," Nelson told KATU. "It is very accessible for anybody to do, and I think that the ease to which that is done and the anonymity in the way the exchange happens, it makes it just too easy."

Nelson believes it sends a message to those who regularly use Backpage to traffic women and children against their will.

"It deters them from that activity," she said. "It's ultimately a win, in my opinion."

For those who voluntarily entered the sex work industry, they say the shutdown puts them in more danger, saying it pushes people out into the street where they’re more likely to experience violence from clients and from the police.

Backpage has said such ads are constitutionally protected free speech.

The seizure has received bipartisan support. Many lawmakers say it's long overdue. It comes just two weeks after the Senate approved bipartisan legislation called the Stop Enabling Sex Traffickers Act. The legislation would create an exception to Section 230, which would pave the way for victims of sex trafficking to hold websites accountable for facilitating abuse.